Jabiru engine failures
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Steady on with recommendations to lean out. There was a lean burn kit a while ago and caused many problems.
A key problem here is not the max or min EGT but the spread.
Those with full monitoring will often see 100 deg C difference in EGT between cylinders. It also changes in different modes of flight
All issues of rich or lean go out the window because you can have BOTH in the one engine at one time. I have seen some where they are fairly even.
Ive too done lots of playing with needles/jets etc and ended up as best I can get. Never over 710 degC, cruising under 690 BUT have sometimes one under 600 at the same time
With CHT, can get them near 120 most of the time, fitting under cylinder deflectors (the gull wings which used be installed on top) certainly stabilised temps and made them easier to manage.
Jabiru USA have a good PDF on air duct "tuning". Fiddly and time consuming but worth it.
Theres some evidence that this variation in fuel distribution is done upstream of carb. work continuing. Not much there so not easy to fix. It has been a thorn for years in carb auto engines too and they are water cooled! strong reason they adapted quickly to port EFI.
Many of the current throughbolt and valve issues are linked to hydraulic lifter introduction, sorry Rutan it wasnt a good move. Keep in mind you still have to open rocker covers anyway to tension headbolts.
A key problem here is not the max or min EGT but the spread.
Those with full monitoring will often see 100 deg C difference in EGT between cylinders. It also changes in different modes of flight
All issues of rich or lean go out the window because you can have BOTH in the one engine at one time. I have seen some where they are fairly even.
Ive too done lots of playing with needles/jets etc and ended up as best I can get. Never over 710 degC, cruising under 690 BUT have sometimes one under 600 at the same time
With CHT, can get them near 120 most of the time, fitting under cylinder deflectors (the gull wings which used be installed on top) certainly stabilised temps and made them easier to manage.
Jabiru USA have a good PDF on air duct "tuning". Fiddly and time consuming but worth it.
Theres some evidence that this variation in fuel distribution is done upstream of carb. work continuing. Not much there so not easy to fix. It has been a thorn for years in carb auto engines too and they are water cooled! strong reason they adapted quickly to port EFI.
Many of the current throughbolt and valve issues are linked to hydraulic lifter introduction, sorry Rutan it wasnt a good move. Keep in mind you still have to open rocker covers anyway to tension headbolts.
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Many of the current throughbolt and valve issues are linked to hydraulic lifter introduction, sorry Rutan it wasnt a good move. Keep in mind you still have to open rocker covers anyway to tension headbolts.
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But Andrew, how do you know where on the lean curve each of the cylinders on these engines is running now?
Also, you would be departing from the configurations which have at least had extensive testing and use to something which has probably had very little.
MAYBE it has been shown that you can't damage a Continental/Lycoming by being too lean. Even if true I don't believe that applies to all engines.
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rutan-around
Your theory that large capacity turbo compound engines increase there o/h from military to cilivan is in correct.
I have stated before this. The r985 for example had a 300 o/h life in the milTary. We had an o/h life of 1700 hours tbo with our engines. We never had one engine failure nor one cylinder failure nor one engine that never made tbo. We never ran lop.
Military have one thing over cilvil use. That is they have unlimited funds. This still is evident today.
To say they made extra hours because they ran lop is completely false and misleading.
We ran over 30000 hours with our engines.
Stop being a sheep. Go look up original P&W o/h times. Btw when they had a problem during the war the engine was removed and sent back to the USA they didn't fix very much at all.
Your theory that large capacity turbo compound engines increase there o/h from military to cilivan is in correct.
I have stated before this. The r985 for example had a 300 o/h life in the milTary. We had an o/h life of 1700 hours tbo with our engines. We never had one engine failure nor one cylinder failure nor one engine that never made tbo. We never ran lop.
Military have one thing over cilvil use. That is they have unlimited funds. This still is evident today.
To say they made extra hours because they ran lop is completely false and misleading.
We ran over 30000 hours with our engines.
Stop being a sheep. Go look up original P&W o/h times. Btw when they had a problem during the war the engine was removed and sent back to the USA they didn't fix very much at all.
Meanwhile, while all you lot are reinventing the lean of peak argument, CASA has taken upon itself the role of judge, jury and executioner once again with no concrete evidence of anything at all except a feeling in its water that Jabiru engines are somehow so "unsafe" that their use, sale and production must be stopped immediately, for make no mistake, that is the likely outcome.
Furthermore, they are trying to set a precedent that would allow them to repeat this action anytime and anywhere they like with zero accountability. At least the SAAA has picked up on this precedent setting danger.
What CASA is doing is retreating from the standard of evidence based regulation in favour of voodoo economics.
To put that another way, you don't get to say "your engine is unsafe". Exactly which model and mod status is unsafe? What are the failure modes and why? Where is the statistical evidence that proves each of these hypothesis? What has the manufacturer proposed to remedy the proven defects? Is their proposal adequate or not? If not, why?
CASA's blanket ukase has to be stopped or it will be used again and again on engines and ultimately aircraft.
To put that yet another way, don't Vans aircraft have a rotten safety record? Aren't they extremely unforgiving in case of an engine failure? If Jabirus can be banned, why not Vans aircraft?
Having said all that, it appears Jabiru brought this on itself and I have no love for either it or CASA, but I'll be buggered if Rotax and all the others are going to get tarred with the same brush!!
Furthermore, they are trying to set a precedent that would allow them to repeat this action anytime and anywhere they like with zero accountability. At least the SAAA has picked up on this precedent setting danger.
What CASA is doing is retreating from the standard of evidence based regulation in favour of voodoo economics.
To put that another way, you don't get to say "your engine is unsafe". Exactly which model and mod status is unsafe? What are the failure modes and why? Where is the statistical evidence that proves each of these hypothesis? What has the manufacturer proposed to remedy the proven defects? Is their proposal adequate or not? If not, why?
CASA's blanket ukase has to be stopped or it will be used again and again on engines and ultimately aircraft.
To put that yet another way, don't Vans aircraft have a rotten safety record? Aren't they extremely unforgiving in case of an engine failure? If Jabirus can be banned, why not Vans aircraft?
Having said all that, it appears Jabiru brought this on itself and I have no love for either it or CASA, but I'll be buggered if Rotax and all the others are going to get tarred with the same brush!!
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Your theory that large capacity turbo compound engines increase there o/h from military to cilivan is in correct.
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Sunfish makes a good point. The Jabiru thing is very general no model, serial numbers. Built between. Then you have the CVD case - CVD pilots are getting restrictions. No new evidence to support.
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Radix, it is a common misconception that CASA have an obligation to foster aviation in Australia. They don't, it's not mentioned anywhere in their Charter and certainly not practiced anywhere in the field.
CASA are the cops. They hate aeroplanes and pilots like cops hate crims. They'd be perfectly happy just to regulate UAV's.
CASA are the cops. They hate aeroplanes and pilots like cops hate crims. They'd be perfectly happy just to regulate UAV's.
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Radix said:-
.
Get hold of the turbo compound operating manual written by Norman Rice based on material supplied by Wright Aeronautical Division.
It is called ' Basic theory of operation turbo compound engine'
If your local technical library can't source it you could always splash out and attend the next Advanced Pilots Seminar and get the book free. You might also learn a lot more about internal combustion engines. It's win win really because if you feel you didn't get your money's worth they will give you a full refund and you walk away with a free book.
I don't claim to know more about their engines than their engineers but I do claim to know a better way to operate their engines than that written in their operating manual by their marketing department. When the operating manuals are written by engineers the engines will last twice as long as they do now but that wouldn't make the sales department happy would it?
.
I'd be interested in a link to actual data rather than hear say.
It is called ' Basic theory of operation turbo compound engine'
If your local technical library can't source it you could always splash out and attend the next Advanced Pilots Seminar and get the book free. You might also learn a lot more about internal combustion engines. It's win win really because if you feel you didn't get your money's worth they will give you a full refund and you walk away with a free book.
Continental and Lycoming have been extremely successful in producing reliable engines so to say you understand more about their engines than they do is a bit arrogant. (Only a bit)
Again, this is what is so hilarious about these "arguments" (which aren't arguments at all).
So the all-knowing manufacturers produce a POH that says: "Lean the mixture and note the point that the temperature peaks and starts to fall. Increase the mixture until the EGT shows a drop of 25 degrees F below peak on the rich side of peak." (Quote from a real POH.)
I keep asking this question of the "experts" like yr right contributing to this thread, and keep getting no answer: How does the pilot know if all cylinders of an engine adjusted in that way are running rich of peak?
The fact that the pilot is blissfully ignorant of where the cylinders that aren't driving the EGT guage are on the lean curve doesn't stop them from being at peak, or lean or peak or richer than 25 rich of peak.
I suppose it raises the philosophical question: if a cylinder is running LOP in the forest, does anbody hear?
Maybe CHT depends on whether the pilot knows if the cylinder is running LOP: hotter CHT if she knows; cooler if she doesn't.
Data produced from the operation of tens of thousand engines operated for millions of hours shows the relationship between EGT and CHT. Those data show that CHT will be cooler at 25 LOP than at 25 ROP.
But nooooooo. Your clys will be cooked and your wings will drop off if you operate at 25 LOP instead of 25 ROP!
It's hilarious.
So the all-knowing manufacturers produce a POH that says: "Lean the mixture and note the point that the temperature peaks and starts to fall. Increase the mixture until the EGT shows a drop of 25 degrees F below peak on the rich side of peak." (Quote from a real POH.)
I keep asking this question of the "experts" like yr right contributing to this thread, and keep getting no answer: How does the pilot know if all cylinders of an engine adjusted in that way are running rich of peak?
The fact that the pilot is blissfully ignorant of where the cylinders that aren't driving the EGT guage are on the lean curve doesn't stop them from being at peak, or lean or peak or richer than 25 rich of peak.
I suppose it raises the philosophical question: if a cylinder is running LOP in the forest, does anbody hear?
Maybe CHT depends on whether the pilot knows if the cylinder is running LOP: hotter CHT if she knows; cooler if she doesn't.
Data produced from the operation of tens of thousand engines operated for millions of hours shows the relationship between EGT and CHT. Those data show that CHT will be cooler at 25 LOP than at 25 ROP.
But nooooooo. Your clys will be cooked and your wings will drop off if you operate at 25 LOP instead of 25 ROP!
It's hilarious.
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The turbo compound engines fitted to B29s and Super Constellations went from 200 hrs- 600 hrs time between overhauls when run rich of peak EGT to 3,600 hrs time between overhauls when run lean of peak.
Mmmm not sure how many B29s etc used in cilivan use ?
And not all big turbo compound engines used lop all the time ether. You can not compare apples to oranges or lyc cont to large cap P&W or wright engines. Example of the r985 was an example only of the difference between mil tbo and cilivan. Sorry you could not see that. Back now to tuning pianos
The turbo compound engines fitted to B29s and Super Constellations went from 200 hrs- 600 hrs time between overhauls when run rich of peak EGT to 3,600 hrs time between overhauls when run lean of peak.
Mmmm not sure how many B29s etc used in cilivan use ?
And not all big turbo compound engines used lop all the time ether. You can not compare apples to oranges or lyc cont to large cap P&W or wright engines. Example of the r985 was an example only of the difference between mil tbo and cilivan. Sorry you could not see that. Back now to tuning pianos
C'mon people, stay focussed.
What can be done to appease CASA and perhaps save Jabiru?
My suggestions:
If the MTBF is 1500 hours, immediately impose a 750 hour TBO, or at least a top at 750 hours. Factory should offer this for cost of parts only and a nominal labour charge. If they were really pro active they would do it at a fixed price on a sliding scale according to the hours that the engine had already flown, ie cheap for 750 hours, more if the engine was nearer 2000 hours.
New production engines to fit gaskets, go back to solid lifters, better valves and a better fuelling system e.g. throttle body injection, multi point CHT and EGT probes as standard.
Jabiru to implement a reasonable core trade-in program, even if the old core is not much more than scrap.
Factory to offer a free operator training course with all purchases and after any factory overhaul. Extended warranty and TBO to those who attend.
If they can't warrant the product for at least three years or 750 hours and if they can't get the TBO up to that offered by Rotax maybe they need to shut their doors, as clearly the product is not 'fit for purpose'.
I fear the demise of Jabiru if they do any less.
Other suggestions?
What can be done to appease CASA and perhaps save Jabiru?
My suggestions:
If the MTBF is 1500 hours, immediately impose a 750 hour TBO, or at least a top at 750 hours. Factory should offer this for cost of parts only and a nominal labour charge. If they were really pro active they would do it at a fixed price on a sliding scale according to the hours that the engine had already flown, ie cheap for 750 hours, more if the engine was nearer 2000 hours.
New production engines to fit gaskets, go back to solid lifters, better valves and a better fuelling system e.g. throttle body injection, multi point CHT and EGT probes as standard.
Jabiru to implement a reasonable core trade-in program, even if the old core is not much more than scrap.
Factory to offer a free operator training course with all purchases and after any factory overhaul. Extended warranty and TBO to those who attend.
If they can't warrant the product for at least three years or 750 hours and if they can't get the TBO up to that offered by Rotax maybe they need to shut their doors, as clearly the product is not 'fit for purpose'.
I fear the demise of Jabiru if they do any less.
Other suggestions?
Last edited by Mach E Avelli; 19th Nov 2014 at 20:57.
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I think your all talking about the R3350 lads 
And just for Yr rights benefit they were run around 0.4lb/hp/hr and for a low compression ratio engine that is what? LOP or ROP? please tell me, just in case I forgot something 
MACH E,
The things you mention
are all good improvement ideas. The valves I think are fine. It is more a matter of the valve guide material, and the head distorting affecting guide/seat geometry. Perhaps even rocker arm geometry. These are the things that break heads off valves usually.
And just for Yr rights benefit they were run around 0.4lb/hp/hr and for a low compression ratio engine that is what? LOP or ROP? please tell me, just in case I forgot something MACH E,
The things you mention
it gaskets, go back to solid lifters, better valves and a better fuelling system e.g. throttle body injection, multi point CHT and EGT probes as standard
All good ideas.
Some ideas I like and some I've added.
Perhaps -
- Reduced TBO
- Core replacement at a fair price to get old engines out of circulation
- Reduced margin parts for these upgrades
- Release of affected serial numbers where possible
- Enforcement for owners (this is a major issue and one of the reasons for breakages - many of those that broke had not been upgraded)
- A cooling "kit." New baffles and ducts, something scientific and tested, that is a bolt on "fix." People like a "fix" or a "kit" to solve their problems
- Plenum chamber as an option for cooling like a real Lycoming style one
As for engine components
- Valves that don't warp
- Valve spring washers that don't break
- Thru bolts and nuts that fit
- Increased quality control through known-good suppliers (do they have a QA manager?)
I don't beleive head gaskets are a solution, they would just mask an existing issue.
Some ideas I like and some I've added.
Perhaps -
- Reduced TBO
- Core replacement at a fair price to get old engines out of circulation
- Reduced margin parts for these upgrades
- Release of affected serial numbers where possible
- Enforcement for owners (this is a major issue and one of the reasons for breakages - many of those that broke had not been upgraded)
- A cooling "kit." New baffles and ducts, something scientific and tested, that is a bolt on "fix." People like a "fix" or a "kit" to solve their problems
- Plenum chamber as an option for cooling like a real Lycoming style one
As for engine components
- Valves that don't warp
- Valve spring washers that don't break
- Thru bolts and nuts that fit
- Increased quality control through known-good suppliers (do they have a QA manager?)
I don't beleive head gaskets are a solution, they would just mask an existing issue.
What can be done to appease CASA and perhaps save Jabiru?
Is there a problem at all?
All machines break. Are Jabiru engines failing at a higher rate than other engines, or are there more Jabiru engines operating more hours, and the rate of failure has remained the same? It may be that the rate has remained the same, but there are more failures because there are more engines operating more hours.
Even if the rate of failure has increased, is that a problem? Have there been any serious injuries, fatalities or property damage? If not, what is the “problem”, other than the cognitive bias of punters?
2. Assuming there is a problem, determine a thing called the “cause”.
If some of the folklore-driven thinking evident in this thread is typical of the approach that will be taken by the manufacturer and CASA, Jabiru is, as a business, as good as dead. Let’s hope against hope that it isn’t the approach taken.
My suggestion would be to get people like Oracle1, jabba and his APS off-sider, on the job. They understand how engines actually work and how to actually operate them. Then you might have a better chance of nailing down the actual cause of the problem – if there is one – and options for actually dealing with it.
But aviation regulatory decisions in Australia are often unhindered by inconvenient considerations like facts and cause.
We need to be careful to distinguish between "top end" overhauls and leaking valves.
Top end overhauls include new pistons, cylinder honing, conrod bearings and valves amongst numerous other components.
Jabiru valves cost $45 versus $285+ for a Rotax valve. Lapping in some valves on a Jabiru at a few hundred hours whilst not ideal is not of major financial disadvantage to an owner, but it's not a top end overhaul.
CASA comparing Jabiru failures to Rotax is floored given the reliability of the Rotax. It's a high bar to jump.
Top end overhauls include new pistons, cylinder honing, conrod bearings and valves amongst numerous other components.
Jabiru valves cost $45 versus $285+ for a Rotax valve. Lapping in some valves on a Jabiru at a few hundred hours whilst not ideal is not of major financial disadvantage to an owner, but it's not a top end overhaul.
CASA comparing Jabiru failures to Rotax is floored given the reliability of the Rotax. It's a high bar to jump.